Japanese Patent Laid-Open No. 52-131204 discloses a conventional variable displacement swash plate type compressor (hereinafter, described as a compressor). In the compressor, suction chambers, discharge chambers, a swash plate chamber, and a plurality of cylinder bores are formed in a housing. In the housing, a drive shaft is rotatably supported. In the swash plate chamber, a swash plate that is rotatable by rotation of the drive shaft is provided. Between the drive shaft and the swash plate, a link mechanism is provided. The link mechanism allows change of an inclination angle of the swash plate. Here, the inclination angle refers to an angle of the swash plate to the direction orthogonal to a drive shaft axis of the drive shaft. In the respective cylinder bores, pistons are accommodated reciprocally. A conversion mechanism is constructed to cause the respective pistons to reciprocate in the cylinder bores at a stroke corresponding to the inclination angle by rotation of the swash plate. Further, an actuator changes the inclination angle. A control mechanism controls the actuator. The control mechanism has a pressure regulating valve.
The link mechanism has a lug member, a hinge ball and a link. The lug member is fixed to the drive shaft in the swash plate chamber. The hinge ball is disposed in a center of the swash plate with the drive shaft being inserted therethrough. The hinge ball and the actuator are engaged with each other at the drive shaft axis side, that is, the center of the swash plate. The link is provided between the lug member and the swash plate. The swash plate is pivotably connected to the lug member via the link.
The actuator has a lug member, a movable body, and a control pressure chamber. The movable body is inserted through the drive shaft, and moves in a drive shaft axis direction to be able to change the inclination angle. The control pressure chamber is defined by the lug member and the movable body, and moves the movable body by an internal pressure.
In the compressor, the control mechanism allows the discharge chamber and the control pressure chamber to communicate with each other by the pressure regulating valve, and thereby the pressure in the control pressure chamber is increased. Thereby, the movable body moves in the drive shaft axis direction to press the hinge ball. Therefore, in the compressor, the swash plate pivots on the hinge ball in a direction to decrease the inclination angle. In this manner, in the compressor, a discharge capacity per one rotation of the drive shaft can be decreased.
However, in the above described conventional compressor, the hinge ball and the actuator are engaged with each other in the center of the swash plate. Therefore, in the compressor, a stroke in the drive shaft axis direction of the movable body at the time of the actuator pressing the hinge ball becomes large. Therefore, in the compressor, the length of shaft cannot help making long in order to secure the stroke.
Thus, it is conceivable to define in the swash plate a top dead center corresponding portion as a portion corresponding to atop dead center of the respective pistons and a bottom dead center corresponding portion as a portion corresponding to a bottom dead center of the respective pistons, and to cause the actuator and the swash plate to engage with each other in a position eccentric to the top dead center corresponding portion side in the swash plate from the center of the swash plate, in the compressor. In this case, the stroke in the drive shaft axis direction of the movable body can be made smaller than in the case in which the actuator and the swash plate are engaged with each other in the center of the swash plate. Thereby, reduction in the shaft of the compressor can be realized.
However, a compression reaction force acts on the rotating swash plate at a posterior side in a rotating direction from the top dead center corresponding portion. Therefore, when the actuator presses the swash plate simply in the position eccentric to the top dead center corresponding portion side, a moment that inclines the swash plate in a direction with a line connecting the top dead center corresponding portion and the bottom dead center corresponding portion as a center of rotation acts on the swash plate. Therefore, hollowing occurs to the swash plate, and on changing the inclination angle, the actuator is difficult to move in the drive shaft axis direction. Therefore, in the compressor in this case, the inclination angle is difficult to change, and controllability is reduced.
The present invention is made in the light of the above described conventional circumstances, and an object of the invention is to provide a variable displacement swash plate type compressor capable of exhibiting high controllability while realizing downsizing in a compressor that changes a discharge capacity by using an actuator.